1. Field of the Invention
The present invention relates in general to an ink package including an ink bag which accommodates ink and which is formed of a flexible material, and an ink detecting apparatus. In particular, the present invention relates to an ink package which permits the ink in the ink bag to be effectively consumed, and an ink detecting apparatus which detects, with high accuracy, so-called “a near empty state” of the ink package wherein the ink in the ink bag will run out in the near future, more specifically, the ink in the ink bag has been reduced to a predetermined amount which is larger, by a predetermined amount, than an empty state of the ink (in which a printing operation is impossible) or an amount of the ink in which a printing operation should be inhibited. The invention also relates to an ink package having a structure that permits the near empty state to be detected with high accuracy.
2. Discussion of Related Art
There is conventionally known an ink-jet recording apparatus adapted to introduce ink accommodated an ink container into a printing head, and eject, toward a recording medium, the ink through a plurality of nozzles formed in the printing head by activating the nozzles in accordance with recording patterns, so that a desired image is formed on the recording medium. On the ink-jet recording apparatus, there is mounted an ink cartridge which includes an ink package accommodating ink.
For instance, JP-A-11-78045 discloses an ink cartridge 3 which includes an ink package 11. The disclosed ink package 11 is in the form of a fluid-tightly closed bag formed of a flexible sheet-like resin material. The ink package 11 is accommodated in a rigid cartridge casing 12. The ink package 11 has opposite major surfaces 11a, 11b which are welded at a peripheral portion 11 so as to provide the closed bag. An ink supply member 6 is sandwiched between the opposite surfaces 11a, 11b at one of opposite ends of the closed bag. The ink supply member 6 includes a rubber member 14 which is pierced with a connecting member 5 in the form of a hollow needle to extract the ink from the ink package 11. When the rubber member 14 is pierced with the connecting member 5, the interior space and the exterior space of the ink package 11 is brought into communication with each other, so that the ink in the ink package 11 is supplied to a printing head 2.
In the disclosed ink package 11, one major surface 11a is bonded and fixed to a flat inner surface 12a of the cartridge casing 12. In the operation of the ink-jet recording apparatus, the ink is ejected from the printing head 2. With a decrease in the ink in the ink package 11 during the operation of the ink-jet recording apparatus, the other major surface 11b of the ink package 11 is deformed in a direction toward the one major surface 11a which is fixed to the flat inner surface 12a of the cartridge casing 12. In a state in which the ink in the ink package 11 is substantially consumed, the ink package 11 is in its contracted state in which the opposite major surfaces 11a, 11b are held in close contact with each other.
In the disclosed ink package 11, the ink supply member 6 is interposed between the opposite surfaces 11a, 11b such that its inner surface located within the ink package 11 is substantially perpendicular to the opposite surfaces 11a, 11b of the closed bag. When the ink in the ink package 11 has been substantially consumed and the opposite surfaces 11a, 11b are held in close contact with each other, there is formed a spacing between the two surfaces 11a, 11b in the vicinity of the inner surface of the ink supply member 6, and the ink undesirably remains in the spacing.
The ink remaining in the spacing described above is left unused, so that the ink in the ink package 11 cannot be used up, deteriorating the efficiency of use of the ink.
There is also known an ink-jet recording apparatus adapted to detect the near empty state of an ink bag installed on the apparatus. For instance, JP-B-6-39161 discloses such an ink-jet recording apparatus adapted to detect the near empty state based on a resistance value between two electrodes which are disposed at one and the other of opposite ends of a flat ink bag such that the two electrodes are opposed to each other. The flat ink bag is disposed in a casing in a horizontal posture such that its opposite flat major surfaces of the ink bag extend in the horizontal direction. In the disclosed apparatus, one of the two electrodes disposed at one of the opposite ends of the ink bag is a hollow ink-extracting needle which extracts ink from the ink bag and the other of the two electrodes is disposed at the other end of the ink bag such that the other electrode is opposed to the hollow needle which is inserted into the ink bag. The ink in the ink bag is consumed during operation of the ink-jet recording apparatus. When the amount of the ink remaining in the ink bag becomes small, the opposite major surfaces (the upper surface and the lower surface) of the ink bag are brought into contact with each other at substantially central portions thereof, whereby the resistance value between the two electrodes is increased. The disclosed apparatus detects or determines the near empty state based on the change of the resistance value.
JP-A-60-131248 discloses an ink-jet recording apparatus adapted to detect the near empty state by obtaining the resistance value between two electrodes which are disposed in parallel with each other and which protrude from one end of the ink bag into the interior space of the ink bag. In the disclosed apparatus, the two electrodes which have respective different lengths and which are covered with insulating tubes except leading end portions thereof are disposed in the ink bag filled with ink, such that the two electrodes are parallel with each other. The ink in the ink bag is consumed in the operation of the ink-jet recording apparatus. The disclosed apparatus is arranged to detect the near empty state at an earlier timing, by obtaining gradual changes of the resistance value between the two electrodes, based on the cross sectional shape of the ink in the ink bag which changes with a decrease in the amount of the ink remaining in the ink bag.
In the ink-jet recording apparatus disclosed in JP-B-6-39161 and adapted to detect the resistance value between the two electrodes which are disposed at one and the other of the opposite ends of the ink bag such that the two electrodes are opposed to each other, the near empty state is detected when the upper surface and the lower surface of the ink bag are brought into contact with each other at the substantially central portions thereof. In this arrangement, when the near empty state is detected, the ink remains at portions of the ink bag in the vicinity of the two electrodes, so that the ink remaining at the portions are undesirably left unused. Thus, the ink cannot be effectively consumed in the disclosed ink-jet recording apparatus.
In the ink-jet recording apparatus disclosed in JP-A-60-131248 and adapted to detect the resistance value between the two electrodes which are disposed in parallel with each other and which protrude from one end of the ink bag, the ink remains only at the above-indicated one end of the ink bag with a decrease in the remaining amount of the ink. However, the apparatus obtains the gradual change of the resistance value with the decrease in the remaining amount of the ink, so that there may a possibility of erroneously detecting or determining the near empty state.